Influence of hybrid nanofluids and heat generation on coupled heat and mass transfer flow of a viscous fluid with novel fractional derivative

Journal of Thermal Analysis and Calorimetry - In this paper, it has been discussed a nonlocal fractional model of viscous nanofluid holding a hybrid nanostructure. Hybridized copper (Cu) and...     

Interference of arsenic trioxide on magnesium dependent polymerization of microtubule proteins

Prevention of microtubule polymerization is considered as one of the promising approaches towards inhibition of cell proliferation, especially in treatment of malignancies. Arsenic trioxide, As₂O₃, is being successfully used in the treatment of human lymphoma, while the mechanism of its therapeutic function is still under investigation. Experiments were designed to determine if indeed As₂O₃ interferes with polymerization of nanotube microtubule. Microtubules were extracted from sheep brain and their interaction with arsenic trioxide was examined by spectrometery. Electrical conductometry of 2 mM MgSO₄ solution containing various concentrations of As₂O₃ was studied in order to determine their possible interaction. Transmission electron microscopy was used to show microtubule structure in the presence of arsenic trioxide. Fluorometric characteristics of tubulin dimer were examined in presence of varying concentrations of arsenic trioxide. It is concluded that arsenic trioxide interacts with Mg²⁺ ion around GTPase site of β-tubulin, resulting enhancement of depolymerization of the microtubule polymer.     

Identification of nonlinear bolted lap-joint parameters by force-state mapping

Joints and fasteners often have a significant effect on the dynamical behaviour of assembled mechanical structures and the analytical prediction of structural responses therefore depends upon the accuracy of joint modelling. Detailed constitutive models that fully describe the behaviour of frictional interfaces are often unduly complicated; in which case simpler phenomenological models having parameters identified from vibration tests may be preferable. Unfortunately the direct measurement of forces transmitted between two contacting surfaces and their relative displacements are not possible in practice and it is therefore necessary to rely on measurements remote from joints. In this paper, the parameters of an assumed nonlinear joint model are identified by force-state mapping from time-domain acceleration records in response to single-frequency excitation close to the first natural frequency. The problem of lack of accessibility for measurement at the joint is overcome by casting the governing equation of the system in modal coordinates so that modal parameters are identified to represent the nonlinear behaviour of the joint. A particular result from the experimental programme is the identification of viscous damping coefficients dependent upon displacement amplitude. The significance of this result is that the complex phenomenon of energy dissipation in lap joints can be represented by a simple analytical model capable of producing accurate results.     

Experimental application of orthogonal eigenstructure control for structural vibration cancellation

Orthogonal eigenstructure control (OEC) is a novel feedback control that is applicable to linear systems. Orthogonal eigenstructure control can minimizes the trial and error by the controller designer. It finds orthogonal vectors to some targeted modes of the structure within the achievable eigenvector set. When the targeted modes are replaced with the orthogonal vectors, it results in a decoupled system or structure that leads to vibration isolation. In this article, experimental application of this control method for active vibration cancellation of a plate is presented. Piezoelectric actuators are used as control actuators and accelerometers are used as feedback sensors. Vibration cancellation in a plate due to 150 Hz sinusoidal disturbance and a wideband disturbance within the range 200-300 Hz are experimentally studied. Since OEC is a model-based control method, system identification techniques are used for estimating the state-space realization of the system model. The effect of tuning the control gain is studied to compensate for the inaccurate system identification or factors that cannot be identified easily but play a major role in vibration of a structure. A finite element model of a plate is considered and the effects of scaling the control gains are investigated. It is shown that there is an allowable region for tuning the control gain without loosing the stability. The result of this analysis is used in the experiment for adjusting the control gains.     

Optical and electronic properties of pure and fully hydrogenated SiC and GeC nanosheets: first-principles study

In this work, the electronic and linear optical properties of pure and fully hydrogenated SiC and GeC nanosheets have been studied using the full potential linearized augmented plane wave method within the density functional theory. Our study on SiC and GeC has confirmed their potential applications in electronic devices. The dielectric tensor is derived within the random phase approximation. The dielectric function, reflectivity, energy loss function and refraction index of these nanosheets for parallel (E||X) and perpendicular (E||Z) electric field polarization directions are well described. It is observed that hydrogenated nanosheets have semiconductor behavior with anisotropic optical spectra for both E||X and E||Z polarization direction. Also, hydrogenated nanosheets provide new electronic transitions between their neighboring atoms.     

Stabilizing network bargaining games by blocking players

Cooperative matching games (Shapley and Shubik) and Network bargaining games (Kleinberg and Tardos) are games described by an undirected graph, where the vertices represent players. An important role in such games is played by stable graphs, that are graphs whose set of inessential vertices (those that are exposed by at least one maximum matching) are pairwise non adjacent. In fact, stable graphs characterize instances of such games that admit the existence of stable outcomes. In this paper, we focus on stabilizing instances of the above games by blocking as few players as possible. Formally, given a graph G we want to find a minimum cardinality set of vertices such that its removal from G yields a stable graph. We give a combinatorial polynomial-time algorithm for this problem, and develop approximation algorithms for some NP-hard weighted variants, where each vertex has an associated non-negative weight. Our approximation algorithms are LP-based, and we show that our analysis are almost tight by giving suitable lower bounds on the integrality gap of the used LP relaxations.     

A new error in variables model for solving positive definite linear system using orthogonal matrix decompositions

The need to estimate a positive definite solution to an overdetermined linear system of equations with multiple right hand side vectors arises in several process control contexts. The coefficient and the right hand side matrices are respectively named data and target matrices. A number of optimization methods were proposed for solving such problems, in which the data matrix is unrealistically assumed to be error free. Here, considering error in measured data and target matrices, we present an approach to solve a positive definite constrained linear system of equations based on the use of a newly defined error function. To minimize the defined error function, we derive necessary and sufficient optimality conditions and outline a direct algorithm to compute the solution. We provide a comparison of our proposed approach and two existing methods, the interior point method and a method based on quadratic programming. Two important characteristics of our proposed method as compared to the existing methods are computing the solution directly and considering error both in data and target matrices. Moreover, numerical test results show that the new approach leads to smaller standard deviations of error entries and smaller effective rank as desired by control problems. Furthermore, in a comparative study, using the Dolan-Moré performance profiles, we show the approach to be more efficient.     

Molecularly imprinted polymer on a SiO2‐coated graphene oxide surface for the fast and selective dispersive solid‐phase extraction of Carbamazepine from biological samples

A surface carbamazepine‐imprinted polymer was grafted and synthesized on the SiO₂/graphene oxide surface. Firstly SiO₂ was coated on synthesized graphene oxide sheet using the sol–gel technique. Prior to polymerization, the vinyl group was incorporated on to the surface of SiO₂/graphene oxide to direct selective polymerization on the surface. Methacrylic acid, ethylene glycol dimethacrylate and ethanol were used as monomer, cross‐linker and porogen, respectively. Nonimprinted polymer was also prepared for comparison. The properties of the molecularly imprinted polymer were characterized using field‐emission scanning electron microscopy and Fourier‐transform infrared spectroscopy. The surface molecularly imprinted polymer was utilized as an adsorbent of dispersive solid‐phase extraction for separation and preconcentration of carbamazepine. The effects of the different parameters influencing the extraction efficiency, such as sample pH were investigated and optimized. The specificity of the molecular imprinted polymer over the nonimprinted polymer was examined in absence and presence of competitive drugs. The carbamazepine calibration curve showed linearity in the ranges 0.5–500 μg/L. The limits of detection and quantification under the optimized conditions were 0.1 and 0.3 μg/L, respectively. The within‐day and between‐day relative standard deviations (n = 3) were 3.6 and 4.3%, respectively. Furthermore, the relative recoveries for spiked biological samples were above 85%.